Optical Fibers Question

It seems that a major concern in the fabrication of optical fibers is hydroxyl diffusion into the fibers. I understand that a high hydroxyl concentration can lead to much higher attenuation. I don't know why though.

Well, "explain", hrmm.... but it has something to do with vibration at least. But as I'm writing it seems odd to me that the optical and vibrational energy scales should overlap...
I think, however, the solution lies in that "optical" fibers actually don't use visible light (the association one, at least I, might get from optical). I think there was something with 1,54 mikrometers, which is rather a large wavelength. Probably this is where hydroxyls absorb into an excited vibration state. Yeah, this seems right. Am however not so eager to check with a calculation for the moment... :zzz: